C-and-Cpp/C2/Functions/English-USA

Time	Narration
00:01	Welcome to the spoken tutorial on Functions in C and C++.
00:06	In this tutorial we will learn,
00:09	What is a function
00:11	Syntax of a function
00:13	Significance of return statement
00:16	We will do this through examples.
00:18	We will also see some common errors and their solutions.
00:22	To record this tutorial, I am using,
00:25	Ubuntu Operating System version 11.10,
00:29	gcc and g++ Compiler version 4.6.1 .
00:35	Let us start with the introduction to functions.
00:39	A function is a self-contained program executing a specific task.
00:45	Every program consists of one or more functions.
00:49	Once executed, the control will be returned back from where it was accessed.
00:55	Let us see the syntax for function.
00:59	ret-type defines the type of data that the function returns.
01:05	fun_name defines the name of the function.
01:09	parameters is the list of variable names and their types.
01:14	We can specify an empty parameter list.
01:18	This is called as functions without arguments.
01:21	And this is called as functions with arguments.
01:26	Let us see a program using void.
01:29	I have already typed the program on the editor.
01:32	So I will open it.
01:35	Note that our file name is function.
01:38	And I have saved the file with the extension .c (dot c).
01:43	Let me explain the code.
01:45	This is our header file.
01:47	Before using any function, it must be defined.
01:51	Here we have defined a function called add.
01:54	Note that add function is without any arguments.
01:58	And the return type is void.
02:01	There are two types of functions-
02:03	User-defined that is our add function and
02:06	Pre-defined that is printf and main function .
02:12	Here we have initialized a and b by assigning them values as 2 and 3.
02:19	Here we have declared a variable c.
02:21	Then we add the values of a and b.
02:24	The result is stored in c.
02:27	Then we print the result.
02:29	This is our main function.
02:32	Here we call the add function.
02:34	The addition operation will be performed and the result will be printed.
02:39	Now click on Save.
02:42	Let us execute the program.
02:45	Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously.
02:53	To compile, type gcc function dot c hyphen o fun.
03:00	To execute, type ./fun (dot slash fun).
03:05	We see the output is displayed as Sum of a and b is 5 .
03:10	Now come back to our program.
03:13	Functions contain special identifiers called as parameters or arguments.
03:20	Let us see the same example with arguments.
03:23	I will change a few things here.
03:27	Type int add(int a, int b)
03:32	Here we have declared a function add.
03:36	int a and int b are the arguments of the function add.
03:41	Let us delete this.
03:43	No need to initialize a and b here.
03:46	Delete the printf statement.
03:49	Type int main()
03:52	Let us declare a variable sum here.
03:54	Type int sum;
03:57	Then type sum = add(5,4);
04:03	Here we call the add function.
04:05	Then we pass the parameters as 5 and 4.
04:10	5 will be stored in a and 4 will be stored in b.
04:14	The addition operation will be performed.
04:18	Let us now print the result.
04:20	Hence type here
04:22	printf(“Sum is %d\n”, sum);
04:27	Delete this, as we have already called the function above.
04:32	Type return 0;
04:36	A non-void function must use a return statement that returns a value.
04:41	Click on Save.
04:43	Let us execute the program.
04:45	Come back to our terminal.
04:48	Now compile the program as before.
04:50	Let us execute.
04:52	The output is displayed as Sum is 9 .
04:57	Now let us see how to execute the same program in C++.
05:02	Come back to our program.
05:04	Let me change a few things here.
05:07	First press Shift, Ctrl and S keys simultaneously.
05:12	Now save the file with .cpp extension.
05:18	Click on Save.
05:19	First we will change the header file as <iostream>
05:24	We will include the using statement here.
05:28	The function declaration is same in C++.
05:32	So there is no need to change anything here.
05:37	Now replace the printf statement with the cout statement, as we use cout<< function to print a line in C++.
05:48	We don't need the format specifier and \n here.
05:52	Delete the comma.
05:54	Now, type two opening angle brackets.
05:58	After sum , again type two opening angle brackets.
06:03	Within double quotes, type backslash n.
06:07	Delete this closing bracket.
06:09	Now Click on Save.
06:11	Let us compile the program.
06:14	Come back to our terminal.
06:16	Type g++ function dot cpp hyphen o fun1
06:23	Here we have fun1, this is because we don't want to overwrite the output file fun.
06:31	Press Enter.
06:34	Type ./fun1
06:38	The output is displayed as: Sum is 9
06:42	Now we will see the common errors which we can come across.
06:47	Suppose here, we type x in place of 4.
06:51	I will retain the rest of the code as it is.
06:55	Click on Save.
06:58	Let us compile the program.
07:02	We see an error at line no. 10.
07:06	'x' was not declared in this scope.
07:09	This is because 'x' is a character variable.
07:13	It was not declared anywhere.
07:15	And our add function has integer variable as an argument.
07:21	So, there is a mismatch in return type and return value.
07:25	Now come back to our program.
07:27	Let us fix the error.
07:30	Type 4 at line no. 10.
07:32	Click on Save.
07:35	Let us execute again.
07:37	Let me clear the prompt.
07:40	Compile the program as before.
07:42	Yes! It is working.
07:45	Now we will see another common error which we can come across.
07:50	Suppose here we pass only one parameter.
07:55	Delete 4.
07:57	Click on Save.
07:59	Switch to the terminal.
08:01	Let us compile.
08:03	We see an error at line no 10.
08:06	too few arguments to function 'int add (int, int)'
08:11	Switch back to our program.
08:14	You can see here we have two parameters
08:19	int a and int b.
08:22	And here we are passing only one parameter.
08:25	Hence it is giving an error.
08:27	Let us fix the error.
08:29	Type 4.
08:31	Click on Save .
08:34	Switch to the terminal.
08:36	Let us execute again.
08:39	Yes! It is working.
08:42	Come back to our slides.
08:44	To summarize, in this tutorial we have learnt -
08:48	function
08:50	Syntax of function
08:52	function without arguments
08:54	Eg- void add()
08:56	Function with arguments
08:58	Eg- int add(int a, int b)
09:02	As an assignment, write a program to calculate the square of a number.
09:07	Watch the video available at the link shown below.
09:11	It summarizes the Spoken Tutorial project.
09:14	If you do not have good bandwidth, you can download and watch it.
09:18	The Spoken Tutorial Project Team:
09:21	Conducts workshops using spoken tutorials,
09:24	Gives certificates to those who pass an online test.
09:28	For more details, please write to, contact@spoken-tutorial.org
09:35	Spoken Tutorial Project is a part of Talk to a Teacher project.
09:40	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
09:47	More information on this Mission is available at the link shown below.
09:52	This is Jean Bonnet from IIT Bombay.
09:55	Thank You for joining.

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